Wireless ad hoc networks allow node-to-node communication without central control or wired infrastructure. Such networks may have dynamic, randomly-changing, multihop topologies composed of wireless data communication links between the nodes. Ad hoc networks are advantageous because they are inexpensive, fault-tolerant, and flexible. Various known methods relate to data transmission within an ad hoc wireless data communication network. However, most known methods do not address self-configuration of wireless nodes for the formation and maintenance of efficient network topology.
Known ad hoc networking methods typically organize the network on the basis of geographic proximity of the nodes or the strength of signals received by the various nodes. Known methods of ad hoc network organization also require nodes to regularly transmit network information to all other nodes in the network, which results in increased radio traffic and interference. Increased radio interference inhibits the formation and maintenance of ad hoc networks having a large number of nodes and requires nodes to transmit at a greater power, which reduces their battery life.
Short range wireless technology utilizing standards based radio technology, such as the Bluetooth radio standard (hereinafter “Bluetooth”), promises to remove price barriers to mobile network use. By doing so, wireless devices are becoming available for applications where wired networks have been impracticable and in which prior wireless communication networks have been too expensive or inflexible. However, while Bluetooth radio technology is an ad hoc networking solution for personal data applications, it provides for only a limited number of communication channels, thereby restricting the number of Bluetooth devices that can communicate over an ad hoc network at any given time.
With regard to asset tracking, wireless data networks are known for use in warehouse management and other asset-tracking applications. However, existing wireless data network technologies are not well suited to asset tracking, which involves a large number of network nodes (e.g., hundreds or even thousands). Furthermore, existing wireless technologies are cost prohibitive, are prone to radio frequency (RF) interference, and consume a large amount of electrical power. Accordingly, wireless data networks are not commonly used in asset tracking.
Another obstacle to widespread implementation of the use of standards based radios, such as Bluetooth radios, especially in asset-tracking applications, is the limited life of the radio due to its power consumption. Each standards based radio associated with an asset being tracked often operates from a battery that is included within the housing of the radio. The battery is able to effectively power the radio for only a short period of time. For example, a Bluetooth radio, whether of the class 1, 2, or 3 type, utilizes about 40 mAh of current when actively receiving transmissions. Even in standby mode, wherein the radio is neither receiving nor transmitting but is in a low power consumption mode from which it can quickly return to an active state, such a radio utilizes about 10 mAh of current. Bluetooth radios therefore can be expected to last less than about ninety (90) days, and only half that long in fairly active asset-tracking applications.
In view of the foregoing, it will be apparent that certain needs exist: for an improved low cost networking technology that has the benefits of the price and flexibility of standards based radios, but that overcomes the limited networking capacity of this technology; for more efficient methods of forming, organizing, and maintaining ad hoc wireless networks; and for a wireless data network technology that accommodates a large number of nodes, reduces RF interference, and consumes less power. A need also exists for a standards based radio device that consumes less power when awaiting the receipt of transmissions, thereby increasing the effective useful life of the radio device. The present invention addresses one or more of these needs.